In Ashkenazi siddurs God's name is spelled with two yuds; in Sephardi siddurs we find them spelled as YKVK with the word a-d-o-n-o-y placed inside the last "hey". Also, on occasion, God's name (YKVK) gets three extra vavs.

Is there a reason for this type of printing of God's name in Sefardi siddurs?

I believe the extra vavs are only there as vowels. I've seen the Name spelled out with different vowels under each letter, and the vavs just seemed two special instances of that (shuruk and cholom malei).
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Charles KoppelmanAug 7 '13 at 0:59

4 Answers
4

I don't know about the extra Vavs (do you have an example?), but the YKVK/adonoi is fairly straightforward -- it's a reminder to have in mind both the meaning of YKVK, i.e. "G-d was, is, and will be" (i.e. G-d is above time), and the meaning of "Adonoi" -- "G-d is master of all." (And if you can't focus on both, I believe the latter intent is the most important one, given how we pronounce it.) I've seen it in some siddurim called "Kavanot Hashem" -- what to concentrate on when pronouncing G-d's name.